Planar and ultrathin liquid crystal (LC) polarization optical elements have found promising applications in augmented reality (AR), virtual reality (VR), and photonic devices. In this paper, we give ...a comprehensive review on the operation principles, device fabrication, and performance of these optical elements. Optical simulations methods for optimizing the device performance are discussed in detail. Finally, some potential applications of these devices in AR and VR systems are illustrated and analyzed.
Planar optics based on patterned cholesteric liquid crystals (CLCs) has attracted increasing attention owing to the self‐organized helical structure and the ability to create arbitrary reflected ...wavefront through spatial orientation control. However, because of the subwavelength‐orientation requirement, it is challenging for liquid crystal lens to achieve a low f‐number (f/#) and large deflection angle simultaneously. Furthermore, with the increasing demand for compact size in novel optical systems, reflective lens has advantage over the transmissive one because it can fold the optical path. Here, a new off‐axis reflective polarization volume lens (PVL) with f/# = 0.825, large aperture size, simple fabrication process, thin profile, circular polarization selectivity, and large diffraction angle is proposed. In contrast to traditional vertical spiral structure, PVL is based on patterned CLCs with a slanted helical axis. In this paper, the PVL is theoretically evaluated and then three reflective PVLs at red, green, and blue wavelengths (R = 605 nm, G = 532 nm, and B = 450 nm) are fabricated. Meanwhile, a simple approach is utilized to achieve 20 mm diameter and 16.5 mm focal length. The low scattering and good image quality of reflective PVL enrich these functional devices and provide promising applications to novel foldable optical systems and waveguide‐based wearable near‐eye displays.
A reflective polarization volume lens (rPVL) with f‐number = 0.825 and 45° off‐angle, operating at reflective type and visible range, is presented here. Patterned cholesteric liquid crystal method, combined with interference exposure strategy, is utilized to realize subwavelength orientations and large size. Reflective imaging in different central wavelengths with off‐angle paves the way for practical use of rPVL in novel optical systems.
With rapid advances in high-speed communication and computation, augmented reality (AR) and virtual reality (VR) are emerging as next-generation display platforms for deeper human-digital ...interactions. Nonetheless, to simultaneously match the exceptional performance of human vision and keep the near-eye display module compact and lightweight imposes unprecedented challenges on optical engineering. Fortunately, recent progress in holographic optical elements (HOEs) and lithography-enabled devices provide innovative ways to tackle these obstacles in AR and VR that are otherwise difficult with traditional optics. In this review, we begin with introducing the basic structures of AR and VR headsets, and then describing the operation principles of various HOEs and lithography-enabled devices. Their properties are analyzed in detail, including strong selectivity on wavelength and incident angle, and multiplexing ability of volume HOEs, polarization dependency and active switching of liquid crystal HOEs, device fabrication, and properties of micro-LEDs (light-emitting diodes), and large design freedoms of metasurfaces. Afterwards, we discuss how these devices help enhance the AR and VR performance, with detailed description and analysis of some state-of-the-art architectures. Finally, we cast a perspective on potential developments and research directions of these photonic devices for future AR and VR displays.
Abstract
Presently, liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays are two dominant flat panel display technologies. Recently, inorganic mini-LEDs (mLEDs) and ...micro-LEDs (μLEDs) have emerged by significantly enhancing the dynamic range of LCDs or as sunlight readable emissive displays. “mLED, OLED, or μLED: who wins?” is a heated debatable question. In this review, we conduct a comprehensive analysis on the material properties, device structures, and performance of mLED/μLED/OLED emissive displays and mLED backlit LCDs. We evaluate the power consumption and ambient contrast ratio of each display in depth and systematically compare the motion picture response time, dynamic range, and adaptability to flexible/transparent displays. The pros and cons of mLED, OLED, and μLED displays are analysed, and their future perspectives are discussed.
A simple yet general swelling–deswelling microencapsulation strategy has been developed to achieve well dispersed and intimately passivated crystalline organic–inorganic perovskites nanoparticles ...within polymer matrixes and results in a series of highly luminescent CH3NH3PbBr3 (MAPbBr3)–polymer composite films with unprecedented water and thermal stabilities and superior color purity.
We analyze the color performance and system efficiency of three commonly employed liquid crystal display modes with a blue LED-pumped red and green quantum dots (QDs) backlight. Based on the measured ...QD emission spectra, we can achieve 115% color gamut in CIE 1931 and 140% in CIE 1976 color space, while keeping the same energy efficiency as conventional backlights. Next, we apply multi-objective optimization method to refine the QD emission spectra and find a fundamental tradeoff between display system efficiency and color gamut. This systematic photometric analysis also provides useful guidelines for further optimizing QD backlight design and display system efficiency.
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